Abstract not found

This paper examines, by computational simulation, a canonical Richtmyer-- Meshkov instability realized within the confines of a shock-tube as a planar shock interacts with a co-planar density interface formed by the contact between two gases, air and sulfur hexafluoride (SH 6 ) (Vetter & Sturtevant 1995). Slight perturbations or irregularities in the density interface, for example local deviations from co-planarity, form the density misalignments required to initiate RMI during shock interaction. A second and much more energetic RMI occurs after the initial shock has traversed the extent of the shock-tube, reflected o# the tube end and reshocks the now greatly distorted interface

A Virtual Test Facility (VTF) for studying the three-dimensional dynamic response of solid materials subject to strong shock and detonation waves has been constructed as part of the research program of the Center for Simulating the Dynamic Response of Materials at the California Institute of Technology. The compressible fluid flow is simulated with a Cartesian finite volume method and treating the solid as an embedded moving body, while a Lagrangian finite element scheme is employed to describe the structural response to the hydrodynamic pressure loading. A temporal splitting method is applied to update the position and velocity of the boundary between time steps. The boundary is represented implicitly in the fluid solver with a level set function that is constructed on-the-fly from the unstructured solid surface mesh. Block-structured mesh adaptation with time step refinement in the fluid allows for the e#cient consideration of disparate fluid and solid time scales. We detail the design of the employed objectoriented mesh refinement framework AMROC and outline its e#ective extension for fluid-structure interaction problems. Further, we describe the parallelization of the most important algorithmic components for distributed memory machines and discuss the applied partitioning strategies. As computational examples for typical VTF applications, we present the dynamic deformation of a tantalum cylinder due to the detonation of an interior solid explosive and the impact of an explosion-induced shock wave on a multi-material soft tissue body.

This short article describes flow parameters, numerical method, and animations of the fluid dynamics video LES of an Inclined Jet into a Supersonic Cross-Flow. Helium is injected through an inclined round jet into a supersonic air flow at Mach 3.6. The video shows 2D contours of Mach number and magnitude of density gradient, and 3D iso-surfaces of Helium mass-fraction and vortical structures. Large eddy simulation with the sub-grid scale (LES-SGS) stretched vortex model of turbulent and scalar transport captures the main flow features: bow shock, Mach disk, shear layers, counter-rotating vortices, and large-scale structures. Flow description Helium is injected through an inclined round jet into a supersonic air flow (Fig. 1). In the present investigation, the jet axis forms a 30 ◦ angle with the streamwise direction of the air flow. The flow parameters of air and helium are reported in Table 1. The jet diameter, d, is 3.23×10 −3 m, and the boundary layer thickness, δ, of the air flow is 2×10 −2 m, as in the experimental study of Maddalena, Campioli & Schetz (2006). The air free-stream Mach 1 number is 3.6, the jet Mach number is 1.0, and the jet to free-stream momentum ratio, q, is 1.75. The Reynolds number of the air flow based on the momentum thickness is Reθ = Ueθ/νw = 13 × 10 3 (Reδ = Ueδ/νw = 113 × 10 3), where Ue is the free-stream air velocity and νw is the kinematic viscosity of air computed at the wall for adiabatic wall conditions.